Conventionally, anodic oxidation treatments have been frequently used, in which an anodic oxidation coating is formed on the surface of an aluminum alloy, a substrate, such that the corrosion resistance (the corrosion resistance to hot gases) and the wear resistance or the like are provided to the substrate. For example, a vacuum chamber used in a plasma treatment apparatus of the semiconductor production equipment and various components equipped inside the vacuum chamber, such as an electrode, are mainly formed by an aluminum alloy; however, the corrosion resistance and the wear resistance thereof cannot be maintained as far as the aluminum alloy is of a solid aluminum alloy. Therefore, an anodic oxidation treatment is typically performed on the substrate made of an aluminum alloy so that an anodic oxidation coating (hereinafter, sometimes simply referred to as a “coating”) is formed on the surface of the substrate. That is why, inside the vacuum chamber, the certain processing is performed on a member to be treated, such as silicon wafer, by using various types of corrosive gases and plasmas under a high temperature environment ranging from room temperature to 200° C. or more, in a pretreatment process or a production process of the semiconductor production; thereby the inner face of the vacuum chamber and the various components equipped inside the vacuum chamber, such as a plasma electrode, are exposed to the environment stated above, resulting in that the corrosion resistance and the wear resistance thereof cannot be maintained as far as the aluminum alloy is of a solid aluminum alloy.
As aluminum alloy members in which the above anodic oxidation coating is formed, many members are proposed in which commercially available aluminum alloys, such as an Al—Mg based alloy (JIS A5000 series) and an Al—Mg—Si based alloy (JIS A6000 series), are used as substrates (see, for example, Patent Documents 1 to 7). However, in recent years, the gaseous environments adopted have been more severe due to increased temperatures of the gases and the high-density growth of plasmas, as semiconductors have been highly integrated; hence, the durability of a coating (the corrosion resistance and the crack resistance under a high temperatures) has been often insufficient when an aluminum alloy that is commercially available as stated above, is used as a substrate. In addition, even when the durability of a coating is sufficient, there have been problems in that, because elements that have been added into the aluminum alloy substrate and impurity elements are contained in the coating, and because these elements are emitted in the gas from the coating, members to be treated are contaminated.
On the other hand, from a point of view of reducing the contamination of members to be treated, many aluminum alloys have been proposed as materials for substrates on which an anodic oxidation treatment is performed, in which Mg and Si are added into a highly pure aluminum and contents of impurities are reduced as less as possible (see, for example, Patent Documents 8 to 14).
Further, as an aluminum alloy substrate on which a coating excellent in the durability can be formed, substrates have been proposed in which Mn, Cu, and Fe in addition to Mg and Si are added into a highly pure aluminum (see, Patent Documents 15 and 16). However, because Cu and Fe, which could be contamination sources, are contained in the above aluminum alloy substrates, a sufficient effect cannot be expected for reducing the contamination of members to be treated, and there is also a problem in that the durability of the coating is insufficient under current gaseous environments adopted. In addition, there has been a problem in that the growth rate of an anodic oxidation coating is very slow on the aluminum alloys, resulting in the poor productivity.
[Patent Document 1] Japanese Patent No. 2900822
[Patent Document 2] Japanese Patent No. 2943634
[Patent Document 3] Japanese Patent No. 2900820
[Patent Document 4] Japanese Patent Laid-Open No. Hei 11-1797
[Patent Document 5] Japanese Patent Laid-Open No. Hei 11-140690
[Patent Document 6] Japanese Patent Laid-Open No. Hei 11-229185
[Patent Document 7] Japanese Translation of Unexamined PCT application No. 2000-282294
[Patent Document 8] Japanese Patent No. 3249400
[Patent Document 9] Japanese Patent Laid-Open No. 2004-99972
[Patent Document 10] Japanese Patent Laid-Open No. 2002-241992
[Patent Document 11] Japanese Patent Laid-Open No. 2002-256488
[Patent Document 12] Japanese Patent Laid-Open No. 2003-119539
[Patent Document 13] Japanese Patent Laid-Open No. 2003-119540
[Patent Document 14] Japanese Patent Laid-Open No. 2003-171727
[Patent Document 15] Japanese Patent No. 3746878
[Patent Document 16] Japanese Patent Laid-Open No. 2001-220637